*{
    margin: 0;
    padding: 0;
}
body{
    background-color: #f7f7f7;
}
nav{
    background-color: gray;
    width: 100%;
}
nav div{
    width: 1200px;
    margin: 0 auto;
    height: 75px;
}
nav div a{
    display: block;
    float: left;
}
nav ul{
    list-style: none;
    width: auto;
}
nav div:after{
    content: "";
    display: block;
    clear: both;
}
nav ul:after{
    content: "";
    display: block;
    clear: both;
}

nav ul li{
    float: left;
    padding-top: 35px;
    margin: 0 5px;
}
nav ul li a{
    display: inline-block;
    text-decoration: none;
    height: 40px;
    color: orange;
    font-size: 18px;
    font-weight: 600;
    line-height: 30px;
    padding: 5px 10px;
}
.active a{
    display: inline-block;
    background-color: white;
    height: 40px;
    color: orangered;
    font-size: 18px;
    font-weight: 600;
    line-height: 30px;
    padding: 5px 10px;
}
nav ul li a:hover {
    background-color: orangered;
    text-decoration: none;
    color: white;
}
section{
    width: 1200px;
    margin: 0 auto;
    background-color: white;
}
section iframe{
    width: 100%;
    height: 600px;
    border: none;
    padding: 20px 10px;
}